1. Field of the Invention
The present invention relates to a fiber stub, an optical module including the fiber stub, an optical transmitter including the optical module, and an optical communication system including the optical transmitter.
2. Related Background Art
Optical modules for supplying signal light to optical fibers have widely been in use in optical communication systems such as optical LAN. Such an optical module is placed within an optical transmitter. In general, an optical module has a semiconductor laser system and an optical system for guiding laser light from the laser system to an external optical fiber. As the laser system, a semiconductor laser device of Fabry-Perot type or DFB type can be used. In addition, an external cavity semiconductor laser system may also be used. In the external cavity system, a semiconductor optical amplifying device and a Bragg grating constitute an optical cavity.
Examples of optical modules using an external cavity semiconductor laser system are disclosed in Electronics Letters, Jun. 20, 1991, vol. 27, No. 13, pp. 1115–1116, Japanese Patent Application Laid-Open No. HEI 6-5961, Publication WO94/22187, and Japanese Patent Application Laid-Open No. 2000-353845. Each of the optical modules disclosed in Publication WO94/22187 and Japanese Patent Application Laid-Open No. 2000-353845 has a pigtail fiber. The fiber has a fiber Bragg grating. The grating and a laser diode within the module constitute an optical cavity.
In the art, it is desired to downsize optical modules and optical transmitters. It is also important to improve their mass-productivity.